Telephone system



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17 Sheets-Sheet 1'7 UNITED Price Y 2,020,458 TELEruoNn srs'rEM Jack F.Dahl, Millburn,

Telephone Laboratories,

York, N. Y., a

N. J., assigner toV Bell incorporated, New

corporation of New York Application June 9, 1934, Serial No. 729,782

21 Claims. (Cl. 179-27) This application relates to telephone systemsand more particularly to telephone systems in which the establishment oiconnections involves more than one operator.

More speciiically, the invention relates to a modication of theoperators equipment disclosed in Patent No.,1,753,3l8 granted to J. B.Newsom, April 8, 193() in which the operators equipment is located at acentralized oice in which no switching takes place. In such anarrangement, while automatic ringing is used at the terminating oice, itis desirable for'certain types of calls to place the start of ringingunder the control of the originating operator. Depending on the natureof the call being handled, the operator may or may not wish to talk withthe called party. Heretoiore it has been necessary for the originatingoperator to await a signal indicating that the called line has beenreached before she could operate her ringing key. In accordance with thepresent invention, the originating operator may operate her ringing keyas soon as she has passed the wanted line number to the control operatorand the ringing signal is thereupon held in abeyance until theconnection has been completed at which time it becomes effective tostart the machine ringing equipment.

In trunking systems, such as the present, where an alternating currentrelay is connected across the trunk line to respond to an application ofringing current to initiate machine ringing,rthe surges of directcurrent which take place in the trunk due to disconnections, etc. areoften sufcient to operate the ring-up relay falsely. To obviate thisdiniculty, in accordance with the present invention, the ring-up relayhas two differentially wound windings which are connected in series withcondensers, one to each side of the line, the opposite ends of thewindings being connected to battery and ground. The ring-up relay istherefore responsive to ringing current applied to either side of theline but is unaffected by surges which occur over the two sides of theline.

The operators equipment used at the centralized office includes a, linkcircuit which interconnects the register sender and the trunk. Timingmeans is associated with the link circuit for giving an alarm if any ofthe functions of the -equipment is delayed unduly. Normally, this timingmeans causes the transmission of a signal to the trunk which in turntransmits the signal to the originating operator and releasesthe-operating equipment. However, in the case of a link circuitsuspected of faulty operation, means is provided whereby' the operationof the timing means prevents the release' of one or more parts oi theequipment so that the cause of the trouble 'may be determined. At acertain stage of the operation only the link circuit is held and in thatcase the signal to the originating operator is not given. The signaltransmitted to the trunk circuit causes the disconnectionof the outgoingsupervisory relay from the trunk conductors and its connection to asource of battery and interrupted ground so that the supervisory signalat the originating office is intermittently operated as a reordersignal.

A clearer understanding of the invention will15`-i` be obtained from aconsideration of the following description in connection with theaccompanying drawings in which:

Fig. 1 shows in diagrammatic form the circuits shown in detail in theremaining drawings.

Figs. 2 andV 3 show Athe relay equipment of trunks of two types. l

Figs; 4to 8 and 11 show the link circuit for connecting the operatorsposition equipment and sender with the trunk equipment.

Figs. 9 and 10 show the incoming selector in which the trunk of Fig. 3terminates.

Figs. 11-A, 12, 14 and 15 show the sender.

Fig. 13 shows the position circuit.

- Figs. 16 and 17 show the incoming selector in 30` which the trunk ofFig. 2 is terminated; and

A Fig. 18 shows the manner in which the remaining figures are to bearranged.

Referring first to Fig. 1, the equipment at four telephone offices isdisclosed, that is, equipment at office A, at a toll or long distanceoice O, a centralized ofce B and a terminating ofce T. The centralizedequipment at ofce B -may be employed in the completion of toll callswhich, having been extended from the calling substation it@ at a localcnice A to a toll operators position at the office O, may be furtherextended by means of jack iti, cord 02 and jack |03 to the long distancetrunk circuit I5() at the centralized office B. The establishment of aconnection. with the trunk circuit causes the linkcircuit lEZ toassociate itself with the trunk, with the position circuit 15d and withthe sender E53. The link circuit first connects the incoming end of thetrunk with the position circuit so that the toll operator may give thewanted number to the B operator. It then connects the position circuitwith the sender to permit the registration of the number in the senderand then connects the sender with the outgoing end of the 55 trunk sothat the sender may control the incoming selector |10 and the finalselector |1| in the selection of the wanted line |12.

The centralized equipment may also be used subscriber reaches the Aoperator'over the dial equipment indicated by line inder II I and thetrunk terminating in the plug I2. The insertion of plug ||2 in jack ||3results in the seizure of trunk |5| and the same operations of thecentralized equipment as for the long distance trunk. Trunk I5I ispermanently connected to incoming selector which differs from theincoming selector I 10 in which the long distance trunk |50 terminated.However, rlnal selectors IBI and |1| may be of the same type. Theincoming selectors |10 and |80 have .been shown as located at the sameterminating oflice. However, it is to be understood that while eachtrunk passing through the centralized B oilce connects a particularoriginating oice with a particular terminating oiiice, each of aplurality of originating oilices may be connected to a plurality ofterminating oflices'by groups of trunks which may be served by thecentralized B oiice equipment.

Incoming toll call Referring now-to the detailed drawings, thesubscriber at substation 200 in originating a call for a subscriber atsubstation |180 will be connected by suitable equipment with a longdistance operators position having access through the centralized Boiiice with the oce at which substation |160 is located.

When the long distance operator inserts the calling plug of her cord 202in the jack 203 leading to the trunk circuit of Fig. 2, a circuit isclosed from battery through the right winding of relay 2| 9, resistance2| I, right back contact of relay 2|0, lower left winding of repeatingcoil 204, over the ring conductor of the incoming inter-oilice trunk andthrough the repeating coil and supervisory relay in the long distanceoperators cord (not shown), back over the tip conductor to the upperleft winding of repeating coil 204, left back contact of relay 2 I0,resistance 209 to ground through the left winding of relay 2|9. Rel-ay 2I9 closes van obvious circuit for relay 2| 4 which in turn operatesrelay 2|3. Both relays 2| 4 and 2| 3 are slow to release to prevent afalse release of the connection in case the incoming end of the trunkcircuit is opened momentarily. Relay 2|4 also connects ground over itsright front contact, right back contact of relay 2| 5, to resistance 2|1in shunt of the winding of relay 2|8 to prevent its premature operation.In addition, relays a circuit from ground over the right contact ofrelay 2|4, back contact of relay 2|2, left front Contact of relay 2| 3,right winding of relay 2I0 to battery. Relay 2|0 closes a holdingcircuit for relay 2| 9 extending fromv battery through the right windingof relay 2|9, resistance 2|I, right front contact of relay 2|0,resistance 209, left winding of relay 2|9 to ground. Relay 2|9 remainsoperated independent of the control of the toll operator until the trunkcircuit is closed through to the incoming selector circuit. Relay 2| 3closes a circuit from ground at the upper normal contact of relay 206,inner right contact of relay 2|3, inner left back contact of relay 22|,winding of relay 222 to battery at the right back contact of relay 225.Relay 222 locks over its inner left :front contact to its operatingground independent of relay 22|.

The operation of relay 222 initiates the association of the trunkcircuit with the operators equipment. It therefore connects ground overits outer left contact and the outer right back contact of relay 22| tothe start conductor 23|. It also connects battery through resistance 234over its inner right front contact and the inner right back contact ofrelay 22| to conductor 232 cuit from battery through the winding ofrelay 220, the middle right contact of relay 222, right back contact ofrelay 226 to conductor 233 which likewise terminates in a terminal ofselector 100.

The connection of ground to conductor 23| completes a circuit whichextends over the normal contact of jack 502, lower back Contact of relay505, back contact of relay 526 through the winding of relay 5| 6 tobattery over the upper back contacts of relay 5| 0. Relay 5|6 operatesin this circuit closing an obvious circuit for the trip magnet 146 ofthe trunk nder. It also closes a circuit from ground over its outerupper front Contact, lower back contact of relay 5| 0, inner lower backContact of relay 483, lower contacts of cam 626 to the winding of relay8|9 and battery, to initiate the operation of the link circuit. Aparallel circuit also extends from conductor 23| through the lowerwinding of relay 509 to battery.

The start circuit of Fig, 5 closely resembles that disclosed in theabove identied Newsom patent and serves to prevent interference betweencalls originating in close succession. Relay 559 controls that part ofthe circuit which acts in case of trouble to delay the handling oi acall to sound an alarm and automatically disable the group of linkcircuits on which the trou.-I ble occurred. Relays 480 to 486 cooperatewith the start circuit and function in case the motors driving a part ofthe trunk nders stop running. Fig. fl also shows portions of three linkcircuits for the purpose of indicating the method of allotting links forservice. This is also disclosed in the above mentioned Newsom patent andwill not be described in detail here.

When relay 8i@ is operated, it locks in a circuit from battery throughits winding, over its inner left front Contact, right contacts of cam 6IQ, left back contact of relay 620 toy ground over commutator strip 1|!and brush 1li). Another holding circuit is also closed for relay I9 overthe lower right and upper left contacts of cam 0 I 9 which extends toground over the commutator strip and brush 135 after the selector movesoff-normal for the purpose of centering the brushes of the selectorproperly. With relay 8|9 operated, a circuit is closed from batterythrough the winding of sequence switch magnet 500, lower right contactof cam 501i, cuter lelt front contact of relay Sig, upper right andlower left contacts of cam SI2 to ground, advancing sequence switch 600from position l. With sequence switch G00 in position 2, a circuit isclosed from battery through the winding of the updrive magnet 1|4, uppercontacts of cam 5 l 2, outer left front contact oi relay 8|9, over thelower right and upper left contacts of cam 608 to ground.

As the selector starts upward, ground is connected over brush 101 andcommutator segment 108, left contacts of cam 69|, to the winding oirelay 5|@ and battery. Relay 5|0 locks over its inner lower frontcontact, left back contact of back contact of ating circuit of relay' ii2@ so long as relay i204 is held operated.

When relay ili operates in the reverse battery fundamental circuit, itcloses a circuit from battery through the right winding of relay iliit,upper left contact of cam i632, lower right contact of cam i553 I, irontcontact of relay il i 5, right contacts of cam ii! to ground over theupper contacts of cam i522. With relay illi operated in position 9 oisequence switch itil!) a circuit is closed from battery through thewinding of sequence switch magnet HUB over the lower left contact ofcain H534, inner left Contact of relay ilfi to ground, advancingsequence switch itilil to position iii and thence to position ii overits normal cam. The reverse battery closure is maintained throughposition ii! to insure the 'operation ci the sender relays, but whensequence switch itil@ reaches position ii, relays ili5 and ilillrelease.

When sequence switch itil@ reached position tl/fx battery through theleft winding of relay Het is connected over the upper contacts of cami625 and the upper back contact of relay iili to the upper leit windingof repeating coil iiiii, and the upper terminal oi condenser iiiii,while the lower terminal o the condenser and the lower lett winding ofrepeating coil @tot are connected over the lower back contact of relayitiiR to ground over the left contacts of cam W33.

When sequence switch iiiilil reaches position i i, battery through theleft winding oi relay ile@ is extended from the upper leit winding oirepeating coil iil over the upper contacts oi iiii to the'tip conductorZii of the inter-cnice trunk. As sequence switch leaves position iii,the ground above traced is disconnected and when the sequence switchreaches position ii, the ring conductor 2432 of the inter-cnice isextended over the upper contacts oi cam itis, lower left winding ofrepeating coil i592?, lower relay les?, right winding ofrelay il to grund over the lower contacts of cam itil. rI'he incoming selector Vnowawaits trunk closure by the link or trunk circuit. Y,

ln the sender when the reverse battery circuit is opened, relays H3@ andiid@ operate in the circuit closed by relay i263. Relay iid@ opens thefundamental circuit in the usual inanner and relay i itt closes acircuit from grounded conductor titi, front contact ci relay littthrough the winding o relay iii to battery over the left front contactoi relay i293. Relay ldt, in operating, opens the locking circuit forrelay itil@ and that relay releases. Relay i255@ also disconnects groundat its leit back contact from conductor li.

The removal of ground from conductor lt! indicating that the sender hascompleted its iunction, opens the circuit of relay tit which nowreleases closing a circuit from battery through the winding oi sequenceswitch magnet tilt, upper left contact of cam ttt, left back contact oirelay Si@ to ground over the lower right contact of cam tiet, advancingsequence switch iil to position 9 trom whence it is advanced to positionil over its local carn. As soon as sequence switch til@ leaves position81/2 ground is disconnected from conductor li releasing relay iilil anddisconnecting ground irom oit-normal conductor it i, thereby releasingall relays which are locked to that conductor and, since it removesground from conductor i222, releasing all oi the register relays andputting the sender in condition to controlA another call.

As sequence switch til'passes through positions i21/2 to IBI/4 a circuitis closed iront the tip conductor 24! of the inter-office trunk whichwas connected as previously traced to battery through the right windingof relay ili over the left alternate contact of relay 226, conductor23l, brush li, middle right Contact of relay Bit, inner right frontcontact of relay Bi through resistance Eil, lower right and upper leitcontacts of cani till, outer right back contact of relay Bill, brushlt?, conductor 238, over the inner left front contact of relay 225through resistance 23!! to the ring conductor 2&2 and thence to groundthrough the left winding of relay il as above traced.

When sequence switch Gti) reaches position i3, battery throughresistance tit is removed from conductor 232 thereby releasing relay 22lbut since relay 223 is still operated, the locking circuit of relays2.2i and 226 is maintained and a circuit is closed from ground over theback contact o relay Ztl, inner right front contact of relay 22%, outerright front contact of relay 2222, through the winding of relay 29E,resistance right back contact of relay 225 to battery. Relay 256, inoperating, closes a locking circuit for itself rorn battery over theback contact of relay resistance 239, winding o relay 2%, outer upperfront contact of relay 2% to ground. Relay disconnects ground from theholding circuit of relay 222 which now releases. Relay 2% also connectsthe tip conductor Zfii of the interoiice trunk over its inner upperiront contact, upper back contact of relay 205, upper right winding ofrepeating coil 2M, back contact of relay 22h, winding of relay 2i2,lower right winding of repeating coil 2M, lower back contact oi' relay2535, inner lower front contact ci relay let to the ring conductor Zl ofthe inter-oce trunk, thereby making a second trunk closure whichoverlaps the trunk closure made by the link circuit.

Relay ilu?, operates in response to the trunk closures by the link andtrunk circuits, completing a circuit from ground over the lower left andupper right contacts oi cam i633, front contact of relay H08, lowercontacts ci cam itat through the winding oi relay Het to battery. Relayilse closes an obvious circuit for relay il which closes a substituteground to the right winding o relay il. It also connects ground over itsinner left front contact, left contacts oi cam iti, upper right contactof cam itl to battery through the winding oi sequence switch magnet iit,advancing the sequence switch to position i2 and in this positionringing and talking take place.

When sequence switch tot leaves position iii, battery through resistanceSi@ is disconnected from conductor 233 thereby releasing relay which inturn releases relays 22! and 22e. The link circuit is thereby completelydisconnected from the trunk circuit.

When sequence switch (itil reaches position iii, a circuit is closedfrom battery through the winding of relay titl, upper contacts of cam @ii, coinrnutator strip lili, brush li2 to ground, Relay iii@ closes acircuit from battery thro-ugh the winding of downdrive magnet lit oi thetrunk nder ltd, left front contact of relay @.i, right contacts of camii to ground, restoring the trunk finder to normal. When the trunkiinder reaches the bottom of its bank, brush li?. leaves coinmutatorstrip lit and relay tit releases, in turn releasing downdrive magnet H5.

